Fluid power steering unit

ABSTRACT

An integral power steering apparatus for the vehicle in which a fluid power piston meshing with a gear sector mechanically connected to the pitman arm accommodates a rotary valve member therewithin which will be actuated to rotate by rotation of a manual steering shaft for controlling the hydraulic pressure supply to assist the piston advancement, whereby a compact and effective power steering unit may be obtained.

O 111 1 1 United States atent 1 1 1 1 3, Suzuki [45] Mar. 27, 1973 [5FLUID POWER STEERING UNIT 3,162,263 12/1964 Brown, Jr. ..91/375 A3,508,467 4/1970 Falkerts ....91/375 A [75 1 Invenmr' Hldek suzuk" AnloJapan 3,602,101 8/1971 Jablonsky et a1. ..91 422 [73] Assignee: AisinSeiki Kabushiki Kaisha, Aichi pref. Japan FOREIGN PATENTS ORAPPLICATIONS 22 Filed; June 1 1971 1,332,115 6/1963 France ..9l/375 121]ApplNo'z 148536 Primary Examiner-Paul E. Maslousky Attorney Pierce,Scheffler & Parker 1 1 Foreign Application Priority Data ABSIRACT .14,1970 .1 ..45 55030 7 une apan An integral power steering apparatus forthe vehicle in [52] US. Cl. ..91/375 R, 91/422 which a fluid powerpiston meshing with a gear sector [51] Int. Cl ..Fl5b 9/10 mechanicallyconnected to the pitman arm accom- 1 1 Field Seam}! 375 380 modates arotary valve member therewithin which will be actuated to rotate byrotation of a manual steering [56] References C'ted shaft forcontrolling the hydraulic pressure supply to UNITED STATES PATENTSassist the piston advancement, whereby a compact and effective powersteering unit may be obtained. 7 3,010,335 11/1961 Foerster et a1...91/380 1 3,033,051 5/1962 Reinke et a] ..9l/375 A 6 Claims, 3 DrawingFigures 71. 77 11 1o 1 72 L 2/0 29 3 32 35 34 g k I k \k e m em; r 1

FLUID POWER STEERING UNIT BACKGROUND OF THE INVENTION This inventionrelates to a power steering apparatus, and more particularly to a fluidpower steering apparatus for the vehicle of the so-called integral typein which the fluid assisted power mechanism is in effect built into thegear housing.

The integral power steering apparatus is advantageous especially for thereasons of the greater convenience at assembly and of the simplearrangement of the fluid piping when the power steering apparatus isinstalled as original equipment on the vehicle as is generally the case.

In spite of the above advantages, difficulties of the in tegral powersteering unit have been encountered in associating with the very limitedspace available in the engine compartment of the automotive vehicle,since it requires a bulkier structure than the linkage type powersteering unit in which the fluid assisted power mechanism is arrangedseparately from the gear housing, the said linkage power steering unitbeing objected to as too complicated at assembly and too difficult ofthe piping arrangement. In order to overcome the above drawbacks,various improved integral power steering apparatus have been presentedone of which accommodates an axially movable spool valve within thepower piston, said spool valve controlling the fluid supply to the fluidchamber in order to assist the piston movement.

However, since the conventional spool valve has been arranged to beshiftable in its axial direction by rotational movement of the steeringshaft, a problem has arisen in that it is necessary to convert the rotational movement of the steering shaft into the axial movement of thecontrol valve member. This requires still much complicated structure ofthe unit and results in unsatisfactory response thereof.

SUMMARY OF THE INVENTION Therefore, an object of this invention is toprovide an integral power steering unit which occupies substantially nomore space than the integral power steering unit heretofore proposed.

Another object of this invention is to provide an integral powersteering unit in which a rotary control valve is housed within acylindrical piston to be actuated by rotation of the steering shaft.

A further object of this invention is to provide an integral powersteering unit which is of a greater ease of manufacture with increasedaccuracy.

The other objects and features, and the novel details of construction ofone commercially practical embodiment of the invention will become moreapparent as this description proceeds, especially when considered inconnection with the accompanying drawings.

BRIEF EXPLANATION OF THE DRAWINGS In the drawings:

FIG. 1 is a section view of the fluid power steering unit according tothe invention taken through the center thereof and illustrating thecomponents of the unit as they are in neutral position. Hydraulic pipingconnection to the fluid pressure source and the reservoir are shownschematically;

FIG. 2 is a section taken on the line II--Il of FIG. 1 and viewed in thedirection of the arrows; and

FIG. 3 is a section taken on the line Ill-III of FIG. 1 and viewed inthe direction of the arrows.

DETAILED DESCRIPTION Referring first to FIG. 1, the numeral 10 denotes agear housing having an inner bore 11, which, on installation of theunit, is fixed to the vehicle frame. The housing is closed at its rightend by a closure plug 12 provided with a first ball bearing assembly 13,a second ball bearing assembly 14 being provided at a bottom end 15 ofthe housing 10. A steering shaft 16 partially provided with a worm l7thereon, therefore, is sup ported and permitted to rotate freely in thehousing 10 by the ball bearing assemblies 13 and 14. Within the bore 1 1of the housing 10, there is slidingly and sealing fitted a hollowcylindrical piston 18 which will divide the bore 11 into two fluidchambers 19 and 20 and accomodate a ball nut 21 hereinafter call nut,and annular inner and outer valve members 22 and 23 therewithincoaxially of the steering shaft 16. The piston 18 is provided with rackteeth 24 meshing with a gear sector 25 integral with a cross shaft 26which extends into the bore 11 and is mechanically connected to aconventional pitman arm (not shown). The nut 21 is internally grooved toseat balls 27 providing the connection between it and the worm 17 of thesteering shaft 16. The axial withdrawal of the nut 21 from the interiorof the piston 18 is limited by an adjuster nut 28 which is externallythreaded to engage the piston 18 and is provided with a fluid passage 29opened to the left fluid chamber 19, but the nut 21 is permitted torotate within predetermined limits relative to the piston 18 in spite ofa spline connection therebetween indicated by the numeral 30. An annulargap 31 is provided between the outer periphery of the nut 21 and theinner cylindrical periphery of the piston 18. Bearings 32 and 33 arepreferably interposed between the piston 18 and the nut 21 and betweenthe adjuster nut 28 and the nut 21, respectively, for decreasing therotational resistance of the nut 21. A pin 34 studded in a sleeve 35 ofthe nut 21 is received in an elongated slot 36 of the inner valve member22 which is biased to the right in FIG. 1 by a coil spring 37 mountedbetween it and the nut 21 thereby permitting the inner valve member 22to rotate in unison with the nut 21.

The outer valve member 23 is prevented both from its rotation relativeto the piston 18 by a pin 38 studded therein and from its axial movementrelative to the piston 18 by an internal shoulder 39 of the piston 18and a snap ring 40 fixed to the piston 18 and a spacer 41 interposedbetween the snap ring 40 and the edge of the outer valve member 23. InFIG. 2, the outer valve member 23 is at its inner cylindrical surfaceaxially grooved at circumferentially equal distances as indicated by thenumerals 42 to 47, while it is at its outer peripheral surface radiallygrooved at axial distances as indicated by the numerals 48 to 51. Theaxial grooves 42, 44, and 46 of the outer valve member 23 communicatedwith the radial groove 49 by throughholes 52, 53, and 54 provided in theouter valve member 23 at circumferentially equal distances,respectively, whilst the axial grooves 43, 45, and 47 communicate withthe radial groove 50 by through holes 55, 56, and 57 atcircumferentially equal distances, respectively. The outer valve member23 is provided with through holes 58 to 60 at circumferentially equaldistances to communicate with the annular grooves 48 of the outer valvemember 23, the holes 58 to 60 being positioned between the axial grooves42 and 43 of the outer valve member 23, between the axial grooves 44 and45 thereof, and

. between the axial grooves 46 and 47, respectively. The

outer valve member 23 is further provided with through holes 61 to 63 atcircumferentially equal distances to communicate with the annular groove51 of the outer valve member 23, the holes 61 to 63 being positionedbetween the axial grooves 43 and 44, between the axial grooves 45 and46, and between the axial grooves 47 and 42, respectively. Each end ofthe axial grooves 42 to 47 in the outer valve member 23 is closed byrings 64 and 65 securely fitted thereto.

The piston 18 is provided with a first radial hole 66 fluidicallycommunicating with the annular groove 48, an axial passage 67fluidically communicating both with the first hole 66 and with theannular gap 31, a second radial hole 68 fluidically communicating withthe annular groove 49, a third radial hole 69 fluidically communicatingwith the annular groove 50, a fourth radial hole 70 fluidicallycommunicating with the annular groove 51, an axial passage 71fluidically communicating with the fourth hole 70 and with the rightfluid chamber 20. An axial hollow 72 is formed in the outer peripheralsurface of the piston 18 to communicate fluidically both with the secondradial hole 68 of the piston 18 and with a pump 73 through an inlet port74 of the housing and an inlet conduit 75, while another axial hollow 76(see FIG. 2) is formed therein at a distance from the axial hollow 72 tocommunicate fluidically with the third radial hole 69 of the piston 18and with a fluid reservoir 77 through an outlet port (not shown) of thehousing 10 and an outlet conduit 78, the said reservoir 77 alsofluidically communicating with the pump 73 through a fluid conduit 79.

The inner valve member 22 of substantially cylindrical shape is axiallygrooved as indicated by the numerals 80 to 85 (FIG. 2). Ridges 86 to 91of the inner valve 22 are arranged at circumferentially equal distancesand are sealingly slidable on the inner cylindrical surface of the outervalve member 23 thereby permitting the axial grooves 80 to 85 therein toface selectively the through holes of the outer valve member 23.

In FIG. 3, within a chordal bore 92 formed in the piston 18 there isslidably fitted a cylindrical spool 93 provided at its intermediateportion with an annular groove 94 in which a radial projection 95 of theinner valve member 22 is received. The cylindrical spool 93 is preventedfrom its axial withdrawal by spacers 96 and 97 and snap rings 98 and 99fixed to the piston 18. Bolts 100 and 101 are fixed to the spacers 96and 97 by nuts 102 and 103, respectively, at their outer ends, whilebeing loosely supported by washers 104 and 105, respectively, at theirinner ends, each of the washers 104 and 105 contacting the inner wallsof the cylindrical spool 93. A coil spring 106 is mounted between thespacer 96 and the washer 104 while a coil spring 107 is mounted betweenthe spacer 97 and the washer 105, thus permitting the inner valve member22 to occupy its neutral position as clearly shown in FIGS. 2 and 3 whenno force is applied on the steering shaft l6.

In operation, when no force is applied on the steering shaft 16, theinner valve member 22 is set in its neutral position so that the sixaxial grooves 80 to 85 in the inner valve member 22 will communicatewith all of the axial grooves 42 to 47 in the outer valve member 23.Thus, the fluid under pressure from the pump 73 flows to the axialgrooves 80 to 85 in the inner valve member 22 through the inlet conduit75, the inlet port 74 of the housing 10, the axial hollow 72 in thepiston 18, the second radial hole 68 in the piston 18, the annulargroove 49 in the outer valve member 23, the through holes 52 to 54, andthe axial grooves 42, 44, and 46 therein. The fluid supplied to theaxial grooves 80 to 85 in the inner valve member 22 will then flow tothe left fluid chamber 19, to the right fluid chamber 20, and to thereservoir 77, respectively, thereby causing no pressure differencebetween the fluid chambers 19 and 20 and hence no axial movement of thepiston 18 due to the hydraulic pressure. More specifically, the fluid inthe axial grooves 80, 82, and 84 in the inner valve member 22 flows tothe left fluid chamber 19 through the through holes 58 to 60 in theouter valve member 23, the annular groove 48 therein, the first hole 66in the piston 18, the passage 67 thereof, the annular gap 31 between thenut 21 and the piston 18, and the passageway 29 in the adjuster nut 28;the fluid in the axial grooves 81, 83, and 85 in the inner valve member22 flows to the right fluid chamber 20 through the through holes 61 to63 in the outer valve member 23, the annular groove 51 therein, thefourth hole in the piston 18, and the axial passage 71 therein; thefluid in the axial grooves to in the inner valve member 22 flows to thereservoir 77 through the through holes 56 to 57 in the outer valvemember 23, the annular groove 50 therein, the third hole 69 in thepiston 18, the axial hollow 76 therein, the outlet port (not shown) ofthe housing 10, and the outlet conduit 78.

When the steering shaft 16 is rotated in a certain direction, forexample in the counterclockwise direction, the nut 21 is urged to rotatein the same direction through the balls 27 provided between it and theworm 17 since there exists a large friction on the pitman arm (notshown) and hence on the cross shaft 26 and the rack teeth 24 on thepiston 18 engages the cross shaft 26 thereby preventing the axialmovement of the piston 18. Therefore, the inner valve member 22 fixed tothe nut 21 by the pin 34 is also rotated in the same direction againstthe exerting force of the spring 106 so that each of the axial grooves80, 82, and 84 in the inner valve member 22 is fluidically communicatedboth with the pump 73 and with the left fluid chamber 19 whilst each ofthe axial grooves 81, 83, and 85 therein is fluidically communicatedboth with the reser voir 77 and with the right fluid chamber 20. As aresult, the piston 18 will be urged to move in the right direction inFIG. 1 due to the hydraulic pressure difference between the bothchambers 19 and 20 thereby causing the clockwise rotation of the crossshaft 26. It

will be seen that the inner valve member 22 is kept in its rotationallyshifted position as long as the steering shaft 16 is being rotated.

When the rotational operation of the steering shaft 16 is halted, theinner valve member 22 is returned to its neutral position by the spring106 thereby interrupting the pressurized fluid supply to the left fluidchamber 19. Thus, a further advancement of the piston 18 will belimited. When the steering shaft 16 is rotated in the clockwisedirection, the pressurized fluid will be supplied to the right fluidchamber 20 thereby causing the axial movement of the piston 18 in theleft direction in FIG. 1, but the detailed explanation in this case maybe omitted since it would be apparent to those skilled in the art.

It should be noted that upon hydraulic failure of the unit the splineconnection 30 between the nut 21 and the piston 18 can effect theendwise movement of the piston 18 thereby permitting the manualoperation of the unit.

Iclaim:

1. A fluid power steering unit comprising a gear housing, a supply pipeto said housing, a discharge pipe from said housing, a cross shaftextending within said housing and formed with a gear sector, a manuallyoperable steering shaft extending within said housing, a hollowcylindrical piston slidably fitted within said housing and delineating apair of opposed fluid chambers therewithin, said piston being providedwith rack teeth meshing with said gear sector of said cross shaft, aball nut housed within said piston coaxially of said steering shaft andmechanically connected thereto, an annular outer valve member rigidlymounted in said piston, said outer valve member being provided with afirst annular groove normally fluidically communicating with one of saidfluid chambers, a second annular groove normally fluidicallycommunicating with the supply pipe, a third annular groove normallyfluidically communicating with the discharge pipe, and a fourth annulargroove normally fluidically communicating with the other fluid chamber,said outer valve member being provided with passage communicating withsaid annular grooves, an annular inner valve member housed within saidpiston coaxially of and spaced from said steering shaft and connected.to said ball nut and rotatable therewith, said inner valve member beingrotatable around said steering shaft by said nut thereby cooperatingwith said outer valve member for selective communication with saidpassages by rotation of said steering shaft, and means having a pair ofreturn springs for normally urging said inner valve member to itsneutral position in which no hydraulic pressure difference is generatedbetween said fluid chambers.

2. A fluid power steering unit as claimed in claim 1 wherein said pistonis provided with a chordal bore and said inner valve member is providedwith a radial projection projecting into said chordal bore, and whereinsaid pair of return springs are mounted in said chordal bore on eachside of said projection.

3. A fluid power steering unit as claimed in claim 1 wherein said innervalve member is provided with a slot steerin shaft.

6. A uid power steering unit of claim 1 wherein an open end of saidpiston is closed by an externally threaded adjuster nut which serves toprevent the axial withdrawal of said nut.

1. A fluid power steering unit comprising a gear housing, a supply pipeto said housing, a discharge pipe from said housing, a cross shaftextending within said housing and formed with a gear sector, a manuallyoperable steering shaft extending within said housing, a hollowcylindrical piston slidably fitted within said housing and delineating apair of opposed fluid chambers therewithin, said piston being providedwith rack teeth meshing with said gear sector of said cross shaft, aball nut housed within said piston coaxially of said steering shaft andmechanically connected thereto, an annular outer valve member rigidlymounted in said piston, said outer valve member being provided with afirst annular groove normally fluidically communicating with one of saidfluid chambers, a second annular groove normally fluidicallycommunicating with the supply pipe, a third annular groove normallyfluidically communicating with the discharge pipe, and a foUrth annulargroove normally fluidically communicating with the other fluid chamber,said outer valve member being provided with passage communicating withsaid annular grooves, an annular inner valve member housed within saidpiston coaxially of and spaced from said steering shaft and connected tosaid ball nut and rotatable therewith, said inner valve member beingrotatable around said steering shaft by said nut thereby cooperatingwith said outer valve member for selective communication with saidpassages by rotation of said steering shaft, and means having a pair ofreturn springs for normally urging said inner valve member to itsneutral position in which no hydraulic pressure difference is generatedbetween said fluid chambers.
 2. A fluid power steering unit as claimedin claim 1 wherein said piston is provided with a chordal bore and saidinner valve member is provided with a radial projection projecting intosaid chordal bore, and wherein said pair of return springs are mountedin said chordal bore on each side of said projection.
 3. A fluid powersteering unit as claimed in claim 1 wherein said inner valve member isprovided with a slot and said ball nut is provided with a pincooperating with said slot to rotate said inner valve member when saidball nut is rotated.
 4. A fluid power steering unit of claim 1 whereinsaid inner valve member is provided with ridge means arranged atcircumferentially equal distances to cooperate with axial groove meansof said outer valve member.
 5. A fluid power steering unit of claim 1wherein said nut is externally splined to engage said piston andpermitted to rotate within predetermined limits by said steering shaft.6. A fluid power steering unit of claim 1 wherein an open end of saidpiston is closed by an externally threaded adjuster nut which serves toprevent the axial withdrawal of said nut.